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FORTH-ICS Named Entity Extraction Named Entity Extraction (NEE) is the process of identifying entities in texts and linking them to related semantic resources Useful in many applications: –Annotating documents, Question answering, Results post-processing, … The Semantic Web realization highly depends on the availability of metadata (structured content in general) describing Web content –A NEE system can automate the extraction of structured data from Web content A lot of information about named entities is already available as Linked Open Data (LOD) –The exploitation of LOD by a NEE system can bring wide coverage and fresh information 3 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014

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FORTH-ICS Motivation (1/2) There are many LOD-based tools that support NEE –DBpedia Spotlight, AlchemyAPI, OpenCalais, AIDA, Wikimeta, … Configuring an existing NEE system for building domain specific applications is… challenging ! –Time consuming and laborious even for persons with computer science background –requires many technical skills Existing tools are mainly dedicated to one specific Knowledge Base which is indexed beforehand –thereby, they do not exploit the dynamic and distributed nature of LOD 5 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014

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FORTH-ICS Motivation (2/2) In existing NEE tools, the user (an admin or a developer) cannot easily: –define its own interesting types/categories of entities –update/extend an existing category with additional entities coming from a new Knowledge Base (KB) –Specify how to link the identified entities with semantic resources –Control how to enrich the identified entities, i.e. configure the properties that are useful for a particular application e.g. retrieve images, or a description in a specific language –Inspect whether and how the identified entities are connected not within the document but as entities in general 6 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014

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FORTH-ICS Motivating Example (2/2) Each community of users has different needs –X-Search should support different configurations The needs of a community constantly change –We would like to be able to dynamically change the configuration (at any time, without requiring to redeploy the system) The LOD constantly grows/changes –X-Search should be aware of the “fresh” information 8 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014

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FORTH-ICS Contribution We will see: –A generic model for configuring (dynamically) a LOD-based NEE system which can be exploited by existing NEE systems –X-Link, a fully configurable NEE tool that supports the proposed model and… –The results of a task-based user study –The results of a case study –Lessons learned, limitations, how to cope with the limitations 9 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014

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FORTH-ICS Functionality – Entity Mining and Entity Linking Entity Mining –Using Gate ANNIE –Currently, no disambiguation is applied (when using gazetteers) If an entity name exists in two supported categories, then this entity is returned twice, one for each category. –Fuzzy matching: identification of an entity that does not match exactly an entity in a category’s gazetteer Using configurable edit (Levenshtein) distance that depends on entity name’s length Entity Linking –For a detected entity name, X-Link returns the matching URIs according to the specified template queries 22 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014

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FORTH-ICS Functionality – Entity Enrichment Entity Enrichment a)Retrieve RDF triples According to the specified template queries, or Select one of some predefined (common) types of properties: i) outgoing, ii) incoming, iii) both outgoing and incoming, iv) outgoing in a language, v) both outgoing in a language and incoming b)Inspect the connectivity of the entity URIs within a radius Retrieve and show the triples that connect the entity URIs 23 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014

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FORTH-ICS Configurability Configuration API –X-Link can be dynamically configured (even while a corresponding service is running) –Supported functions: Add a new category (using a resource class or a SPARQL query) Update an existing category (using a resource class or a SPARQL query) Remove a category Change the displayed name of a category Set/change the KBMs of a category Set/change the resource classes, the SPARQL queries and the SPARQL template queries of a KBM Set/change the active categories Set/change the value of radius “r” Set/change if fuzzy matching is allowed and the allowed edit distance percentage 25 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014

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FORTH-ICS Portability The configuration files can be easily exchanged –Their size is relatively small E.g., for supporting 4 categories related to the marine domain, the configuration files have size less than 5MB –The size mainly depends on the number of supported categories and on the number of the named entities in each category X-Link does not store any semantic information (e.g. URIs or RDF triples) –The entity linking and entity enrichment processes are performed at real-time 26 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014

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FORTH-ICS Task-based User Study Purpose: –Test the usability of the proposed approach –Identify usability problems X-Link was deployed as a Web application configured for the marine domain –Identification of Fish Species in a text or Web page –Entity Linking, Entity Enrichment –The administrator can change the configuration through an administration page Target User: An administrator or a developer who wants to use X-Link for building and dynamically configuring an application 29 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014

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FORTH-ICS Task-based User Study – Setting 11 subjects (23-34 years old) with computer science background, and basic knowledge of Linked Data and SPARQL 5-minute demonstration of the application and its functionality Tasks: –(T1) Add a new category of entities –(T2) Update a category –(T3) Specify how to link the identified entities of a category –(T4) Specify how to enrich the entity URIs of a category –(T5) Inspect the connectivity of the entity URIs (for r=1) The endpoint and the required RDF classes/properties are given –Since our objective was not to evaluate the ability of the user to find related semantic information We recorded: –Whether the subjects succeeded to complete each task –The time to successfully accomplish each task 31 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014

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FORTH-ICS Task-based User Study – Scenario 32 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014 Consider that you are the administrator of an application that can identify Fish names (currently supporting only the English language) in Web pages. You have been asked to perform some changes. Specifically, by exploiting DBpedia, the application must also identify European Countries (T1) as well as fish names in Spanish (T2) (because the application will be used mainly by Spaniards). Also, the identified fishes must be linked with resources from DBpedia (T3) and must be enriched with all their outgoing properties (T4). Finally, in order to test that the system has been properly configured, perform entity mining in the Spanish version of Salmon's Wikipedia page and then inspect the connectivity of the identified entities (T5).

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FORTH-ICS Task-based User Study – Questionnaire (Q0) How easy was to configure the system according to the scenario? (Q1) How easy was to add the new category of entities? (Q2) How easy was to update the existing category? (Q3) How easy was to specify how to link the identified entities? (Q4) How easy was to specify how to enrich the identified entities? (Q5) How easy was to inspect the connectivity of the identified entities? (Q6) What was difficult for you during the execution of the scenario? (Q7) How familiar are you with SPARQL? 34 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014

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FORTH-ICS Q0: How easy was to configure the system according to the scenario? Q1: How easy was to add the new category of entities? Q2: How easy was to update the existing category? Q3: How easy was to specify how to link the identified entities? Q4: How easy was to specify how to enrich the identified entities? Q5: How easy was to inspect the connectivity of the identified entities? Task-based User Study – Answers 35 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014 (Q0-Q5) Evaluation of the difficulty in performing the scenario (results from 11 users) (Q6) What was difficult for you during the execution of the scenario: Difficulty in understanding the notion of the SPARLQ template queries Suggestion to provide a user-friendly interface for constructing them (Q7) How familiar are you with SPARQL: 1 (I don’t know SPARQL):0% 218% 336% 436% 5 (I am expert in SPARQL)9%

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FORTH-ICS Case Study: Querying online DBpedia at real-time 36 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014 Purpose: Test the feasibility of the entire approach We measured the time for: –creating a new category –linking an identified entity with semantic resources –enriching an entity URI –inferring the connectivity of the entity URIs We repeated the experiments about 20 times and here we report the average values Data used in the experiments: –http://www.ics.forth.gr/isl/X-Link/files/exper_data.zip The experiments were carried out using an ordinary computer with processor Inter Core i7@3.4Ghz CPU, 8GB RAM, Win7 64bit. Implementation in Java 1.7.

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FORTH-ICS Case Study: Time for adding a new category 37 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014 We used 7 sets of DBpedia resource classes. Each set has 5 different resource classes containing a particular number of entities, i.e. totally 35 different resource classes were used.

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FORTH-ICS Case Study: Time for linking an identified entity 38 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014 We used 8 sets of DBpedia resource classes. Each set has 5 different resource classes containing a particular number of entities, i.e. totally 40 different resource classes were used. For each resource class, we randomly selected 10 labels of entities belonging to that class.

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FORTH-ICS Case Study: Time for inspecting the connectivity 40 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014 We randomly selected URIs of the same resource class from DBpedia and we repeated the experiments for 5 different resource classes.

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FORTH-ICS Lessons Learned – Reliability and Scalability Existing publicly available Knowledge Bases are not reliable –They mainly serve demonstration purposes –Their efficiency and availability change over time –They do not serve multiple concurrent requests If an entity belongs to a category with millions of entities then the linking time can be high –The same is true in case the underlying application requires to retrieve semantic information for numerous entities at once –Caching/Indexing is a solution, but with the cost of loosing the freshness of the results In a real application: –The underlying KBs may not be publicly available –A dedicated Warehouse can be constructed that will serve the application –Distributed infrastructure 41 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014

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FORTH-ICS Conclusion A generic model for configuring (dynamically) a LOD-based NEE system X-Link –A LOD-based, fully configurable, NEE tool that supports the proposed model By adopting the proposed approach one can configure a NEE system within a few minutes The exploitation of LOD can be supported at query-time The major bottleneck is the reliability and performance of online SPARQL endpoints –We expect this limitation to get overcome in the near future –In the meanwhile, we can use caching/indexing/dedicated warehouses/distributed infrastructure 43 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014

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FORTH-ICS Future Research It would be beneficial for the community if every NEE system supported the proposed configuration model »We work on defining an RDF vocabulary with explicit semantics We evaluate approaches for entity disambiguation that are appropriate in our setting We elaborate on methods for ranking the matching URIs in case they are numerous 44 P.Fafalios, M.Baritakis, Y.Tzitzikas | WIMS'14 | Thessaloniki, Greece | June 2014 Argentina, the country Argentina, the fish genus